Imaging methods represent important tools in medical technology. Magnetic resonance tomography (MRT) is distinguished in the field of clinical sectional imaging by high and variable soft-tissue contrasts. A magnetic resonance device may include one or more antennas that may be used in order to send and receive radiofrequency electromagnetic signals. Local receive antennas are detuned during the send phase of the MRT examination. Otherwise, high radiofrequency electrical currents may be induced in said local receive antennas, which on the one hand may disrupt the homogeneity of the excitation and on the other hand may endanger any patient and/or damage the receive electronics.
Hitherto, PIN diodes (positive intrinsic negative diodes) have been used for detuning, by which an inductance or coil is switched parallel to a capacitance or capacitor situated in an antenna circuit. The inductance is dimensioned such that, together with the capacitance, it forms a high-impedance parallel resonant circuit, which in turn suppresses a current flow in the receive antenna. The PIN diodes employed as switches have the advantage that in the conducting state the PIN diodes are able to switch very high radiofrequency currents and in the non-conducting state introduce few losses into the receive antenna. The disadvantages are that in the conducting state relatively high direct currents flow through the PIN diode and that the transition to the non-conducting state is comparatively slow.